1. Field of the Invention
The present invention comprises a video camera or other data acquisition assembly that can be used in downhole environments including, without limitation, in oil and or gas wells. More particularly, the present invention comprises a video camera or other data acquisition assembly that can be installed in a well in order to confirm or validate certain well conditions including, without limitation, structural and equipment integrity, debris and the condition and quality of fluid in a well.
2. Brief Description of the Prior Art
During drilling operations, wells are typically filled with a fluid known as drilling mud, which is also sometimes referred to as drilling fluid; although compositions can vary, such drilling mud frequently includes high concentrations of clays, barites or other solids. In many cases, such drilling mud is pumped down the longitudinally extending bore of drill pipe or other tubular string, and then circulated up the annular space formed between the external surface of said drill pipe and the internal surface of the surrounding casing or open hole wellbore. Such drilling mud serves a variety of functions including, without limitation, to cool and lubricate drill bits and other downhole equipment; to transport pieces of drilled-up rock and other debris from the bottom of a well to the surface; to provide hydrostatic pressure to control encountered subsurface pressures; and to seal porous rock formations with a substantially impermeable filter cake.
After a well has been drilled to a desired depth and casing has been installed, the well is typically completed in one or more producing reservoirs. Prior to such completion operations, the drilling mud (together with any associated drill cuttings, cement pieces and/or other debris) is typically removed from a well and replaced with substantially clear completion fluid, which is typically a weighted brine or other similar liquid. A “clean” wellbore generally promotes a successful completion process and enhanced production/injection performance by minimizing or eliminating fine solids commonly found in drilling mud and are potentially damaging to hydrocarbon producing reservoirs. A “clean” wellbore also minimizes mechanical failures such as packed screens and stuck valves.
Efficient and comprehensive wellbore cleanout (“WBC”) is fundamental to the success of a well completion process, especially in oil and gas wells located offshore or in deepwater or other challenging environments. Such wells typically require a comprehensive wellbore cleanout service to ensure that all drilling mud, cement and/or other debris are fully removed from a well prior to installing expensive and complex completion equipment. Conventional wellbore cleanout operations typically involve a combination of abrasive brushes, scrapers, magnets or other mechanical tools, together with specially designed displacement chemicals.
Currently, the only means of validating the cleanliness of a wellbore and the effectiveness of the fluid displacement process is to run a mechanical debris retrieval tool with a gauge ring, typically on wire line, multiple times until the tool returns to the surface “empty” (that is, with no debris visible). Secondary measures include monitoring and testing of fluid return characteristics. None of these approaches are totally reliable or accurate, and often incorrectly indicate that a wellbore has been cleaned sufficiently, allowing residual drilling mud, cement or other debris to remain within said wellbore. Because this fact is widely known, multiple pipe and wireline trips, and excessive fluid circulation, is typically practiced in order to clean out the wellbore.
Verification of wellbore fluid displacement and resultant “cleanliness” is critically important because it can greatly reduce or eliminate the likelihood of unnecessary pipe or wireline trips in and out of a well. Such unnecessary trips can be extremely expensive, particularly on rigs operating in deep water environments or other remote locations. In addition to economic concerns, such unnecessary pipe or wireline trips create additional safety hazards for personnel. By eliminating unnecessary trips, and especially pipe trips, safety hazards can be significantly mitigated. Alternatively a surface readout or memory downhole video camera could be lowered into the wellbore after the clean out assembly has been pulled from the well to provide this inspection. Albeit this would require 12-24 additional hours or more to complete. In deep water operations this time would increase the cost of the well by as much as $1,000,000, typically not considered an acceptable cost
Thus, there is a need for a means for efficiently and accurately confirming and validating cleanliness of a wellbore including, without limitation, following displacement of drilling mud with completion fluid.